Catherine Zeta-Jones -- Good Genes or Good Docs?

Catherine Zeta-Jones' good looks are nothing to have reservations about.

Here's a 27-year-old version of the "Chicago" star at a movie premiere back in 1996 (left) and 21 years later ... the now 48-year-old mother of two -- and the 'Legend of Zorro' babe backstage at NYFW last month (right).

Fency.

The question is ...